Alternation of Flex Cable Vibration Modes in High Precision Hard Disk Drives

For fast and accurate data accessing operations, flex cable's vibratory response has been identified to be the key development focus for magnetic hard disk drives to meet near nanometer precision accuracy. Dampening the cable's dynamics with damper layers and revising the seek servo designs have been the common approaches found in the literature to reach the requirement. In this paper, vibrations of nonuniform flex cable, which is composed of baseline flex cable layers and addition of piezoelectric layer such as polyvinylidene fluoride film, are investigated through experiments and non-classical, reduced-order finite element analysis. It is found that the addition of the piezofilm changes the cable's natural frequencies only within 3% error range but alters the cable's bending vibration mode shapes significantly. The change in the cable's mode shapes leads to change of the known cable/actuator dynamic coupling reported in the literature. Results presented in this paper establish mechanical framework for active control of the flex cable onto the rotary actuator.